package com.kerraway.config;

import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

/**
 * 以静态变量保存Spring ApplicationContext, 可在任何代码任何地方任何时候中取出ApplicaitonContext.
 * Ref: https://sb33060418.iteye.com/blog/2372874
 *
 * @author 小柯
 * @date 2019/07/18
 */
@Component
public class SpringContextHolder implements ApplicationContextAware {

  private static ApplicationContext applicationContext;

  /**
   * 实现ApplicationContextAware接口的context注入函数, 将其存入静态变量.
   */
  @Override
  public void setApplicationContext(ApplicationContext applicationContext) {
    SpringContextHolder.applicationContext = applicationContext;
  }

  /**
   * 取得存储在静态变量中的ApplicationContext.
   */
  public static ApplicationContext getApplicationContext() {
    checkApplicationContext();
    return applicationContext;
  }

  /**
   * 从静态变量ApplicationContext中取得Bean, 自动转型为所赋值对象的类型.
   */
  public static <T> T getBean(String name) {
    checkApplicationContext();
    return (T) applicationContext.getBean(name);
  }

  /**
   * 从静态变量ApplicationContext中取得Bean, 自动转型为所赋值对象的类型.
   */
  public static <T> T getBean(Class<T> clazz) {
    checkApplicationContext();
    return (T) applicationContext.getBean(clazz);
  }

  /**
   * 清除applicationContext静态变量.
   */
  public static void cleanApplicationContext() {
    applicationContext = null;
  }

  private static void checkApplicationContext() {
    if (applicationContext == null) {
      throw new IllegalStateException("applicaitonContext未注入,请在applicationContext.xml中定义SpringContextHolder");
    }
  }
}  
